System and method for visible and infrared high dynamic range sensing

ABSTRACT

A high dynamic range sensing device is disclosed. The device includes an array of Bayer pattern units. Each of the Bayer pattern units comprises a plurality of pixels and each of the plurality of pixels comprises a plurality of photodiodes. At least one of the plurality of photodiodes in each pixel is configured to detect near infrared (NIR) light and at least one of the plurality of photodiodes in each of the plurality of pixels is configured to detect visible light.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 16/826,004, filed on Mar. 20, 2020, entitled “SYSTEM AND METHODFOR VISIBLE AND INFRARED HIGH DYNAMIC RANGE SENSING,” which is acontinuation of U.S. patent application Ser. No. 15/415,376, filed onJan. 25, 2017, now U.S. Pat. No. 10,638,054, and entitled “SYSTEM ANDMETHOD FOR VISIBLE AND INFRARED HIGH DYNAMIC RANGE SENSING,” thedisclosures thereof incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present application relates to the technical field of image sensor,and more particularly, to visible and infrared high dynamic range (HDR)sensing.

BACKGROUND

Charge-coupled device (CCD) sensors and Complementary Metal-OxideSemiconductor (CMOS) sensors are commonly used for visible and infrared(IR) imaging, of which the dynamic range is an important performanceindicator. The dynamic range can be defined as the ratio of the highestilluminance to the lowest illuminance that an image sensor can measurewith an acceptable output quality. HDR images usually appear crisper andricher than normal images, because of better retention of highlight andshadow details. Capturing HDR images poses great challenges, for thelack of high-performance systems, devices, and methods.

SUMMARY

One aspect of the present disclosure is directed to a high dynamic rangesensing device. The device may be a visible, IR, or visible-IR sensingdevice. The sensing device includes an array of Bayer pattern units.Each of the Bayer pattern units comprises a plurality of pixels. Each ofthe plurality of pixels comprises a plurality of photodiodes. At leastone of the plurality of photodiodes in each pixel is configured todetect near infrared (NIR) light and at least one of the plurality ofphotodiodes in each of the plurality of pixels is configured to detectvisible light.

Another aspect of the present disclosure is directed to anotherembodiment of a high dynamic range sensing device. The device comprisesan array of optical filter combinations. Each of the optical filtercombinations may correspond to a pixel of the sensing device and has atleast two different filters, and each of the optical filter combinationsmay be associated with a plurality of photodiodes.

Another aspect of the present disclosure is directed to a high dynamicrange sensing device. The sensing device comprises an Bayer array ofoptical filter combinations. Each of the optical filter combination maycorrespond to a pixel of the sensing device, and each of the pixel mayhave a plurality of photodiodes.

Another aspect of the present disclosure is directed to a high dynamicrange sensing device. The device may be a visible, IR, or visible-IRsensing device. The device may comprise a plurality of pixels, eachcomprising four photodiodes, and at least one photodiode in one pixelbeing configured to detect near infrared (NIR) light.

Additional features and advantages of the present disclosure will be setforth in part in the following detailed description, and in part will beobvious from the description, or may be learned by practice of thepresent disclosure. The features and advantages of the presentdisclosure will be realized and attained by means of the elements andcombinations particularly pointed out in the appended claims.

It is to be understood that the foregoing general description and thefollowing detailed description are exemplary and explanatory only, andare not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which constitute a part of thisspecification, illustrate several embodiments and, together with thedescription, serve to explain the disclosed principles.

FIG. 1A is a graphical representation illustrating a Bayer unit of asensor in prior art from both top and side views.

FIG. 1B is a graphical representation illustrating a Bayer unit of aQuadrant Pixel HDR sensor from both top and side views, consistent withexemplary embodiments of the present disclosure.

FIG. 2A is a graphical representation illustrating a visualized sensorpixel pattern in prior art.

FIG. 2B is a graphical representation illustrating a visualized sensorpixel pattern with four integration times, consistent with exemplaryembodiments of the present disclosure.

FIG. 3 is a schematic circuit diagram illustrating a HDR sensor system,consistent with exemplary embodiments of the present disclosure.

FIG. 4 is a circuit diagram illustrating a HDR sensor pixel withmultiple sub-pixels and differential integration times, consistent withexemplary embodiments of the present disclosure.

FIG. 5A is a graphical representation illustrating readout timing,consistent with exemplary embodiments of the present disclosure.

FIG. 5B is a graphical representation illustrating readout timing,consistent with exemplary embodiments of the present disclosure.

FIG. 5C is a graphical representation illustrating readout timing forthe HDR sensor in FIG. 4 with four different integration times,consistent with exemplary embodiments of the present disclosure.

FIG. 5D is a graphical representation illustrating readout timing withthree different integration times, consistent with exemplary embodimentsof the present disclosure.

FIG. 5E is a graphical representation illustrating readout timing withtwo different integration times, consistent with exemplary embodimentsof the present disclosure.

FIG. 5F is a graphical representation illustrating readout timing withthree different integration times and binning, consistent with exemplaryembodiments of the present disclosure.

FIG. 5G is a graphical representation illustrating readout timing withtwo different integration times and binning, consistent with exemplaryembodiments of the present disclosure.

FIG. 5H is a graphical representation illustrating readout timing withtwo different integration times and binning, consistent with exemplaryembodiments of the present disclosure.

FIG. 6A is a graphical representation illustrating a Bayer unit of asensor in prior art from both top and side views.

FIG. 6B is a graphical representation illustrating a Bayer unit of aQuadrant Pixel HDR sensor from both top and side views, consistent withexemplary embodiments of the present disclosure.

FIG. 7 is a circuit diagram illustrating a HDR sensor pixel with foursub-pixels and two different integration times, consistent withexemplary embodiments of the present disclosure.

FIG. 8 is a graphical representation illustrating readout timing for theHDR sensor in FIG. 7, consistent with exemplary embodiments of thepresent disclosure.

FIG. 9 is a graphical representation illustrating readout timing for theHDR sensor in FIG. 7 with two different integration times, consistentwith exemplary embodiments of the present disclosure.

FIG. 10 is a flow diagram illustrating a method for HDR sensing,consistent with exemplary embodiments of the present disclosure.

FIG. 11A is a graphical representation illustrating a Bayer unit of aRGB-NIR (Red Green Blue-Near Infrared) sensor from both top and sideviews.

FIG. 11B is a graphical representation illustrating a Bayer unit of aQuadrant Pixel RGB-NIR HDR sensor from both top and side views,consistent with exemplary embodiments of the present disclosure.

FIG. 12 is a schematic circuit diagram illustrating a RGB-NIR HDR sensorsystem, consistent with exemplary embodiments of the present disclosure.

FIG. 13 is a circuit diagram illustrating a RGB-NIR HDR sensor pixelwith multiple sub-pixels and differential integration times, consistentwith exemplary embodiments of the present disclosure.

FIG. 14 is a graphical representation illustrating readout timing forthe RGB-NIR HDR sensor in FIG. 13 with differential integration times,consistent with exemplary embodiments of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments, examplesof which are illustrated in the accompanying drawings. The followingdescription refers to the accompanying drawings in which the samenumbers in different drawings represent the same or similar elementsunless otherwise represented. The implementations set forth in thefollowing description of exemplary embodiments consistent with thepresent disclosure do not represent all implementations. Instead, theyare merely examples of systems and methods consistent with aspectsrelated to the invention as recited in the appended claims.

Conventional approaches for capturing HDR images are not ideal. Somecurrent technologies produce a HDR image by taking multiple shots ofvarious exposure times and combining features from each shot. Suchprocess may take tens of milli-seconds and is prone to motion artifactscaused by movements. Thus, it is desirable to improve the dynamic rangeand image quality through innovations in the sensor architecture.

A claimed solution rooted in semiconductor engineering overcomesproblems specifically arising in the realm of electronic and opticaltechnology. In various embodiments, a sensing device is disclosed tocapture HDR images. The device may comprise an array of optical filters.Each of the optical filters may correspond to a pixel of the sensingdevice, and each of the optical filters may be associated with one ormore photodiodes. Each photodiode may be associated with an integrationtime, and some of photodiodes of the plurality of photodiodes associatedwith one optical filter may have different integration times.

In one example, each pixel includes four photodiodes each coupled to atransistor for controlling an integration time of the photodiode. Thesensing device may further comprise four micro lenses respectivelyassociated with the four photodiodes. The four photodiodes may bedisposed in a two by two configuration under the one optical filter, andthe four micro lenses may be disposed in the same two by two (2×2)configuration above the one optical filter and each configured to directimpinging light to pass through the one optical filter to reach thecorresponding photodiode. Up to four different integration times can beachieved with the disclosed four-photodiode-pixel system.

The disclosed system may apply to visible sensing (detecting visiblelight), non-visible sensing (detecting non-visible light), or acombination of both. For example, each of the optical filters may be anoptical filter combination of two or more optical filters (e.g., a redfilter and a NIR filter). The optical filters only allow light passageof the corresponding wavelength for detection. Thus, RGB-NIR HDR imagescan be captured with the improved quality.

HDR sensing systems, devices, and methods with various integration timesare described with reference to FIGS. 1-5. A simplified HDR sensingsystem with two different integration times is described with referenceto FIGS. 6-10. RGB-NIR HDR sensing systems, devices, and methods withvarious integration times are described with reference to FIGS. 11-14.

FIG. 1A is a graphical representation 110 illustrating a Bayer unit of asolid-state sensor in prior art from both top and side views. Thesolid-state (e.g., CCD, CMOS) sensor is the most common type of sensor:Bayer pattern filter sensor. Such sensor comprises an optical filterarray arranged on top of a square grid of photodiodes to select red,green, or blue light. From the top view, the four pixels of a Bayer unitare shown as four squares, associated with two green filters across, ared filter, and a blue filter. Each pixel or filter may have identicaldimensions of width X. A typical value for width X is 3.0 μm. Eachsquare comprises a circle representing a micro lens (μlens). As shown inthe side view, each optical filter has a μlens disposed above and aphotodiode (PD) disposed below.

FIG. 1B is a graphical representation 120 illustrating a Bayer unit of aQuadrant Pixel HDR sensor from both top and side views, consistent withexemplary embodiments of the present disclosure. Graphicalrepresentation 120 shows four pixels each of width X, the four pixelsforming the Bayer unit. The four pixels may also comprise two greenfilters across, a blue filter, and a red filter respectively. Each pixelmay comprise multiple sub-pixels of width Y. In this figure, each pixelof width X comprises four sub-pixels of width Y. Each sub-pixelcorresponds to a photodiode. Each photodiode is coupled to a switch, forexample a transistor, in a specific example, a charge transferring (TX)transistor, which regulates an integration time of the photodiode. Thesesub-pixels form a four by four checkerboard pattern in FIG. 1B.

From the top view, corresponding to the four pixels in this Bayer unit,four filters each of width X are shown. Two of the filters across aregreen, one is red, and the other is blue. Each pixel is subdivided intofour sub-pixels each of width Y and labeled as L3, L2, L1, or S. Width Yand width X can have various lengths. An exemplary length for Y is 1.5μm, and an exemplary length for X is 3.0 μm. Each of the sub-pixelscomprises a μlens represented by a circle.

Correspondingly shown in the side view, each sub-pixel has a μlensdisposed above the filter and a photodiode disposed below the filter.When light impinges on the sensor, the μlens directs the light/photonsto pass through the filter and then to the photodiode, which generatescharges (e.g., electrons and holes) in response to the light exposure.Movement of such charges creates a current. To determine how muchlight/photons hits the sensor, the current is to be measured. Thecurrents produced by the photon conversion are typically very small,which discourages an accurate direct measurement. Thus, currentintegration is used by setting the voltage across the photodiode to aknown potential, and using the photodiode to collect photons for aperiod of time before the voltage is read out. Longer integration timeallows more charges to be converted. The TX transistor coupled to thephotodiode is used to regulate the integration time of the photodiode.Each photodiode may be associated with a TX transistor. It is alsopossible that two or more photodiodes couple to and share the same TXtransistor.

In this side view, two sub-pixels share an optical filter (OF)—twoμlenses disposed above the filter and two photodiode disposed below thefilter. The optical filters disclosed herein may include, but are notlimited to, color filters and IR filters. IR radiation spans wavelengthsbetween approximately 750 nanometers (nm) and 1 millimeter (mm). Onecommonly used sub-division scheme of IR can include near IR (NIR)(0.75-1.1 μm); mid-IR (MIR) (1.1-30 μm); and far IR (FIR) (30-1,000 μm).Thus, IR filters may include NIR filters, MIR filters, FIR filters, etc.In this specification, some embodiments use NIR as an example. Forexample, the optical filter can be a NIR filter that selects NIR lightor allows NIR light to pass through. In some other embodiments, filtersthat are substantially transparent to ultraviolet (UV) light may be usedfor UV imaging. Corresponding photodiodes sensitive to UV light may beplaced under the UV filters in these types of sensing devices.

Since the side view only shows one row of sub-pixels and each pixel hastwo rows by two columns of sub-pixels according to the top view, eachpixel has one filter shared among the four sub-pixels. That is, in anexemplary 2×2 arrangement, each pixel has four μlenses above a sharedfilter, four photodiodes below the shared filter, and four TXtransistors respectively coupled to the four photodiodes. Thisconfiguration gives the name of Quadrant Pixel sensor. Each μlens may besubstantially aligned with its corresponding photodiode, such that mostof the photons impinging on the μlens can be directed to pass the filterand be detected by the photodiode. FIG. 1B and in association withdetails described in FIG. 2B, FIG. 4, FIG. 6B, and/or FIG. 7 belowdisclose a HDR sensing system, consistent with exemplary embodiments ofthe present disclosure.

As discussed above, in some embodiments, each sub-pixel is connected toa TX transistor for regulating integration times. By this way, thesub-pixels are provided with individually-configurable differentialeffective integration time for generating HDR images with the sensor.The various integration times may be labeled as L3, L2, L1, or S. L3,L2, L1, or S may correspond to four different integration times from thelongest to the shortest. Though FIG. 1B shows four sub-pixels with fourintegration times in each pixel, the number of sub-pixels in each pixelis not limited to four, and any two of the integration timescorresponding to the sub-pixels in each pixel may be the same ordifferent. Each of the integration times may be set in default,configured by users, or otherwise determined. Each of the integrationtimes may also be automatically configured according to luminanceconditions (e.g., a longer exposure time is configured for a darkcondition). Two or more of the integration times may be the same.Further, any of the sub-pixels of the same pixel may be configured tohave integration time L3, L2, L1, or S, or any integration time asconfigured, which should not be limited to the illustrations in figuresherein. Integration time labels L and S in this disclosure are merelyexemplary. Also, in exemplary figures of this disclosure, the grey scaleof each sub-pixel may indicate the corresponding level of integrationtimes for illustration purposes. For example, L3 as having the longestintegration time may appear much brighter than S having the shortestintegration time. Again, the grey-scale illustration of integrationtimes is merely exemplary and not tied to particular sub-pixels.

In some embodiments, since each sub-pixel's integration time can beindividually controlled by the corresponding TX transistor, each pixelcan capture and convert image signals corresponding to four integrationtimes. The integration times may be the same or different. If the pixelhas more individually controlled sub-pixels, the image signals capturedcan correspond to more different integration times. Thus, even in onesensor detection by the disclosed device, each pixel can capturemultiple readings corresponding to different integration levels.Captured signals of short integration time may retain highlight detail(e.g., scenes with bright light) while captured signals of longintegration time may retain shadow detail (e.g., scenes with low light).These signals can be combined to obtain images and are essential toachieve HDR imaging.

Some existing HDR imaging systems (known as exposure bracketing) capturemultiple images with the image sensor, each image having a differentexposure time. This capturing process may take tens of milli-seconds. Inthis case, performing HDR imaging by combining the captured images maygenerate undesirable motion artifacts. The disclosed system can capturemulti-exposure-level images in one exposure detection. Since onedetection takes much less time (e.g., under a few milli-seconds) thanmultiple detections (e.g., tens of milli-seconds), motion artifactscaused by movements can be minimized. In another word, the disclosedsystem can integrate the times-domain HDR function with minimized motionartifact and multiple integration times.

Similarly, each pixel can be divided into any number of sub-pixels ofany shapes, and each sub-pixel can be individually controlled in termsof the integration time, thereby achieving multiple integration timeswithin the same pixel.

Further, the Bayer-pattern described herein may include variousmodifications in addition to those shown in FIGS. 1A, 1B, 2A, and 2B. Insome embodiments, the optical filters in a Bayer-pattern unit mayinclude any color, such as CYGM (cyan, yellow, green, magenta), and RGBE(red, green, blue, emerald), etc. That is, the optical filters are notlimited to red, green, and blue filters. In some embodiments, multiplepixels and corresponding filters in a Bayer-pattern unit may be orientedin various configurations, e.g., rotated by 45 degrees. Therefore, anyincorporation of the claimed aspect to modified Bayer sensor designsstill falls in the scope of this disclosure.

FIG. 2A is a graphical representation 210 illustrating a visualizedsensor pixel pattern in prior art. In this figure, 8 rows (labeled as 0to 7) by 8 columns (labeled as 0 to 7) of 64 square pixels are shown.Similar to FIG. 1A discussed above, each pixel may have a width of X. Infact, representation 210 can be seen as an expansion based onmultiplying representation 110 in rows and columns, forming a checkerboard of pixels. Each Bayer unit of FIG. 2A, consisting of four pixels,is assigned to an integration time: either L (long) or S (short). Everytwo neighboring Bayer units have different integration times. That is,as the Bayer unit of 2×2 four pixels in the top left corner are assignedto L, the next Bayer unit of 2×2 pixels in the same row or column areassigned to S, and so forth. However, since every pixel here has onlyone integration time, two Bayer units are required to capture the sameimage with two integration times, which reduces the image resolutioncompared to a similar normal sensor with a uniform integration timeacross all pixels.

FIG. 2B is a graphical representation 220 illustrating a sensor pixelpattern of four integration times, consistent with exemplary embodimentsof the present disclosure. In this figure, 8 rows (labeled as 0 to 7) by8 columns (labeled as 0 to 7) of 64 square pixels are shown. Similar toFIG. 1B discussed above, each pixel may have a width of X=2*Y, and eachpixel may comprise four square sub-pixels of width Y. So there are atotal of 256 sub-pixels shown in FIG. 2B.

As discussed above with reference to FIG. 1B, each of the sub-pixels canhave an individual integration time L3, L2, L1, or S. By achievingintegration time variations among sub-pixels of the same pixel ratherthan among multiple pixels, the resolution of the sensor shown in thisfigure is not reduced while obtaining HDR images, compared to a similarnormal sensor with a uniform integration time across all pixels and withno subpixels.

FIG. 3 is a schematic circuit diagram illustrating a HDR sensor system300, consistent with exemplary embodiments of the present disclosure.The system 300 may comprise a pixel array 301, a row control circuit302, a column readout circuit 303, and a timing generator and processingcircuit 304. The pixel array 301 may comprise multiple pixels arrangedby row and column and associated circuits, e.g., pixels shown in FIG. 1Band FIG. 2B. Each pixel row is coupled to row control circuit 302, andeach pixel column is coupled to the column readout circuit 303. The rowcontrol circuit 302 may control readout timing in each row, and thecolumn readout circuit 303 may receive pixel signals from each column.The timing generator and processing circuit 304 may control the rowcontrol circuit 302 and the column readout circuit 303 in terms of clocktiming, signal processing, etc. The above circuit is merely exemplary,and other possible variations of circuit control may be implemented.

During one exemplary exposure of the photodiode sensor, the photodiodesin the pixel array 301 convert impinging photons into charges (e.g.,electrons and/or holes). The charges are integrated (collected) incorresponding sensor sub-pixels or pixels. After the completion ofintegration cycle, collected charges are converted into voltages. Thevoltages are supplied to the output terminals and coupled to columnreadout circuit 303. In CMOS image sensors, the charge to voltageconversion is accomplished directly in the pixels themselves. The analogpixel voltage is transferred to the output terminals through variouspixel addressing and scanning schemes controlled by the row controlcircuit 302. The analog signal can also be converted on-chip to adigital equivalent before reaching the chip output.

At the pixel level, corresponding portions of the row control circuit302, the column readout circuit 303, and/or the timing generator andprocessing circuit 304 may be collectively deemed as “the circuitcoupled to the plurality of photodiodes” described below with referenceto FIG. 10.

FIG. 4 is a circuit diagram illustrating a HDR sensor pixel withmultiple sub-pixels and differential integration times, consistent withexemplary embodiments of the present disclosure. The circuit diagram ofFIG. 4 may correspond to a pixel in FIG. 2B described above.

As shown in FIG. 4, dash regions indicate the four photodiodes (PD1,PD2, PD3, and PD4) of the four sub-pixels, each associated with anintegration time (L3, L2, L1, or S). Each of the photodiodes is coupledto a charge transferring (TX) transistor (TX1, TX2, TX3, or TX4), whichmay optionally operate in a pulsed integration mode. Each TX transistoris coupled to a TX control line (e.g. transistor TX1 is coupled toTX01). The row control circuit 302 may provide corresponding chargetransfer control signals through TX01, TX02, TX03, and TX04 shown inFIGS. 4, 5B, and 5C to the gate terminal of each charge transferringtransistor TX1, TX2, TX3, and TX4. For example, a first charge transfercontrol signal TX01 may be provided to charge transferring transistorTX1, a second charge transfer control signal TX02 may be provided tocharge transferring transistor TX2, a third charge transfer controlsignal TX03 may be provided to charge transferring transistor TX3, afourth charge transfer control signal TX04 may be provided to chargetransferring transistor TX4.

The four sub-pixels may share other circuit architectures. For example,the sensor pixel may incorporate a buffer amplifier, typically a sourcefollower (SF) transistor, coupled to the TX transistors. The SF maycouple to a sense line (Vout) through a suitable addressing transistor(also can be called a row select transistor RS). The TX transistors arealso coupled to a charge detection node (FD) (also referred to asfloating diffusion node or floating diffusion region). For example, oneof the source or drain terminal of a TX transistor is coupled to thephotodiode, and the other is coupled to node FD. As shown in FIG. 4, TX1is coupled between photodiode PD1 and the node FD, TX2 is coupledbetween photodiode PD2 and the node FD, TX3 is coupled betweenphotodiode PD3 and the node FD, and TX4 is coupled between photodiodePD4 and the node FD.

The charge detection node FD may be implemented using a region of dopedsemiconductor (e.g., a doped silicon region formed in a siliconsubstrate by ion implantation, impurity diffusion, or other dopingtechniques). The FD region exhibits a capacitance that can be used todetect the charges that has been transferred from photodiodes. Thesignal associated with the detected charges on FD is applied to the gateof source-follower transistor SF and conveyed to row select transistorRS by source-follower transistor SF.

The FD node is couple to a reset transistor (RST) that conductivelycouples the FD node to a voltage reference (VDDA). After the charge tovoltage conversion as described above is completed and the resultingsignal is transferred out from the sub-pixels/pixels through the senseline (Vout), the sub-pixels/pixel can be reset by the RST transistor foraccumulation of new charge. In the example shown in FIG. 4, transistorRS is controlled via line RS0. Transistor RST is controlled via lineRST0. This reset step removes collected charges, but may generatekTC-reset (thermal) noise. The kTC-reset noise is removed from thesignal by the Correlated Double Sampling (CDS) signal processingtechnique in order to achieve the desired low noise performance. CMOSimage sensors that utilize CDS usually require four transistors (4T) inthe pixel, one of which serving as the charge transferring (TX)transistor. It is possible to share some of the pixel circuittransistors among several photodiodes to reduce the pixel size.

In some embodiments, the circuit depicted in FIG. 4 may be a part of thepixel array 301, vertical circuit lines such as Vout and VDDA may coupleto the column readout circuit 303 of FIG. 3, and horizontal circuitlines such as RST0, RS0, TX01, TX02, TX03, and TX04 may couple to therow control circuit 302 of FIG. 3.

FIG. 5A is a graphical representation illustrating readout timing,consistent with exemplary embodiments of the present disclosure. In someembodiments, row addressing or selecting signals RS0, RS1, . . . and RSxeach associates with a corresponding row and may indicate row controlsignals with respect to time. Such row control signals may beimplemented by the row control circuit 302 in conjunction with timinggenerator & processing circuit 304 described above with reference toFIG. 3. Each control signal is represented by a pulse in thecorresponding row. The pulse may indicate a voltage (high) with respectto the base line (low). The vertical dash lines indicate clock cycles.When the control signal is high (between two dash lines), it will turnon the row select transistors on that row, and column read out circuit303 will read out the signals on the row. The rows are read outsequentially one after another from RS0 to RSx. Within one frame, everyrow is read out, so all signals captured by the sensor are read out.Then, the cycle may repeat for the next frame.

FIG. 5B is a graphical representation illustrating readout timing,consistent with exemplary embodiments of the present disclosure. In someembodiments, as shown in FIG. 5B and with reference to FIG. 4, varioussignal lines on the left may be pulsed with respect to time to read outphotodiode signals. For example, as shown in FIG. 5, RS0 is mostly high,and RST0 is pulsed periodically, so that each of the TX01, TX02, TX03,and TX04 signals can be read out individually. For example, TX01, TX02,TX03, and TX04 signals may each be read out when RS0 is high and betweentwo pulses of RST0. SHR (Sample and Hold Pixel Reset Signal) and SHS(Sample and Hold Pixel Signal) are signals provided by the columnreadout circuit 303 and configured to readout the photodiode signals.Before each TX reading as represented by pulses on TX time lines, SHRsignal goes high to hold the reset signal, and after the TX reading, theSHS signal goes high to hold the photodiode signal. Such combination canensure that the TX reading is properly reset and read out.

An exemplary timing diagram of a reading out time for 0^(th) row isdescribed in detail below. When row select signal RS0 for the 0^(th) rowis high, row select transistor RS is turned on, which enables that thecharges on FD and applied on the gate of transistor SF be read out viaVout. In the beginning of this reading out period, the row controlcircuit 302 may provide the reset control signal RST0, which turns onthe reset transistor RST, and resets the charge detection node FD toVDDA level voltage. After reset, the reset control signal RST0 may bedeserted to turn off the reset transistor RST. After the reset processis complete, charge transferring transistor control signal or signals(e.g., TX01) may be asserted to turn on corresponding chargetransferring transistors (e.g., TX1). When transfer transistors (e.g.,TX1) are turned on, the charges that have been generated and integratedby the corresponding photodiodes (e.g., PD1) from the incoming light aretransferred to the shared charge detection node FD. As discussed above,row select transistor RS is turned on, the charges on FD and applied ongate of transistor SF can be read out via Vout. After PD1 is read, nodeFD can be reset, and when TX02 is on, PD2 can be read out. Sameoperations can be carried out for the other photodiodes. The chargetransferring transistors (e.g., TX1, TX2, TX3, and TX4) may be pulsedonce to perform one charge transfer operation or may be pulsed multipletimes to perform multiple charge transfer operations. In a typicalconfiguration, there are numerous rows and columns of image pixels inthe pixel array shown in FIG. 3. When it is desired to read out thevalue of the detected charges (the value of the detected chargesrepresented by the signal at the source of transistor SF, which isconnected to node FD), row select control signals may be asserted, andcorresponding image signals Vout that are representative of themagnitude of the charges on shared charge detection node FD (e.g., animage level voltage from one or more photodiodes PD1, PD2, PD3, and PD4)is produced on output Vout in FIG. 4.

FIG. 5C is a graphical representation illustrating integration timingfor the HDR sensor in FIG. 4 with four different integration times,consistent with exemplary embodiments of the present disclosure. FIG. 5Cshows signal lines for four TX transistors with respect to time,corresponding to four photodiodes of one pixel and corresponding tointegration times L3, L2, L1, and S described above. The TX transistorsmay operate in a pulsed integration mode to exhibit desired differentintegration times for HDR imaging. In this figure, the readout for eachphotodiode starts with the end of a previous TX readout pulse and endswith another TX readout pulse. Within that period, also known as aframe, each TX gate may be associated with an integration time,configurable via clock and timing by the circuits described in FIG. 3.

The voltage across each of the photodiodes and their readout times maybe configured by pulses to the corresponding charge transferringtransistor TX to set the integration times shown in FIG. 5C. In someembodiments, for example TX2(L1) in FIG. 5C, after the read out pulse(e.g., the first pulse in FIG. 5C), the charge transferring transistor(e.g., TX2) can be turned on again by a high voltage on control linesignal TX2(L1), and RST can be turned on again, and charges in thecorresponding photodiode (e.g., PD2) are thrown out from the photodiodethrough the charge transferring transistor TX2 to FD and FD is reset toVDDA through reset transistor RST (referring to FIG. 4). When the chargetransferring transistor (e.g., TX2) is low (turned off), charges areallowed to accumulate on the corresponding photodiode (e.g., PD2) for aperiod of time, shown in FIG. 5C as the integration time. When thecontrol line signal TX2(L1) is pulsed, for example, the pulse at the endof line TX2(L1), the accumulated charges are transferred to node FD, andare read out via SF and RS transistors as the corresponding photodiodesignal. The charge transferring transistors (e.g., TX1, TX2, TX3, andTX4) are controlled individually during one frame between a readout anda previous readout. Here, each photodiode in the pixel corresponding acharge transferring transistor has an integration time configurable by acorresponding charge transferring gate timing as shown in FIG. 5C. Eachintegration time may be set to any length. Thus, according to variousintegration times, the converted charges are different for each of thefour photodiodes, achieving different exposure levels within the samepixel.

As shown above, integration times of four TXs can be controlledindependently to achieve HDR imaging with four different integrationtimes. In some embodiments, it is also possible to achieve threedifferent integration times by setting two photodiodes to have the sameintegration times, or achieve two different integration times by settingtwo photodiodes to have the same integration time and setting the othertwo photodiodes to have another same integration time. Details aredescribed below with reference to FIG. 5D and FIG. 5E. Such flexibilityin integration time configuration can offer more imaging options. Also,the signal charges in the photodiodes can be combined into the FD node(binning) as described below with reference to FIG. 5F, FIG. 5G, andFIG. 5H. The binning method can increase the readout efficiency andsignal to noise ratio.

FIG. 5D is a graphical representation illustrating readout timing withthree different integration times, consistent with exemplary embodimentsof the present disclosure. FIG. 5D is similar to FIG. 5C except that theintegration time length of the photodiode associated with TX4 is set tobe the same as that of the photodiode associated with TX1 (both are L3).Thus, among the four photodiodes associated with TX1, TX2, TX3, and TX4,there are 3 different integration times (correspondingly, L3, L1, L2,and L3).

FIG. 5E is a graphical representation illustrating readout timing withtwo different integration times, consistent with exemplary embodimentsof the present disclosure. FIG. 5E is similar to FIG. 5D except that theintegration time length of the photodiode associated with TX3 is set tobe the same as that of the photodiode associated with TX2 (both are L1).Thus, among the four photodiodes associated with TX1, TX2, TX3, and TX4,there are 2 different integration times (correspondingly, L2, L1, L1,and L2).

FIG. 5F-5H below describe various binning methods, consistent withexemplary embodiments of the present disclosure. Any number ofphotodiode signals can be binned for readout, and one or more groups ofbinning can be implemented within each pixel. FIG. 5F is a graphicalrepresentation illustrating readout timing with three differentintegration times and binning, consistent with exemplary embodiments ofthe present disclosure. FIG. 5F is similar to FIG. 5D except that theintegration time of the photodiode associated with TX4 is shifted toalign in time with that of the photodiode associated with TX1. Thus, thephotodiodes signals associated with TX1 and TX4, having the sameintegration time, can be combined into the FD node (binning) describedin FIG. 4 and thus read out together. Correspondingly shown with arrowsin the insert at the bottom right of FIG. 5F, signals from photodiodeTX1(L3) and photodiode TX4(L3) can be binned (combined for readout).Signals from the other two photodiodes TX2(L1) and TX3(L2) are notbinned with any other photodiode signal because of the difference in theintegration time and read out time. Similarly, any two or morephotodiodes within the same pixel can be binned for signal readout, ifhaving the same integration time and read out time.

FIG. 5G is a graphical representation illustrating readout timing withtwo different integration times and binning, consistent with exemplaryembodiments of the present disclosure. FIG. 5G is similar to FIG. 5Eexcept that the integration time of the photodiode associated with TX4is shifted to align in time with that of the photodiode associated withTX1, and that the integration time of the photodiode associated with TX3is shifted to align in time with that of the photodiode associated withTX2. Thus, the photodiodes signals associated with TX1 and TX4, havingthe same integration time, can be combined into the FD node (binning)and thus read out together; photodiodes readings associated with TX2 andTX3, having the another same integration time, can be combined intoanother FD node (binning) and thus read out together. Correspondinglyshown with darker and lighter arrows in the insert at the bottom rightof FIG. 5G, respectively, signals from the photodiode associated withTX1(L2) and the photodiode associated with TX4(L2) can be binned, andsignals from the photodiode associated with TX2(L1) and the photodiodeassociated with TX3(L1) can be binned.

FIG. 5H is a graphical representation illustrating readout timing withtwo different integration times and binning, consistent with exemplaryembodiments of the present disclosure. As shown in FIG. 5H, thephotodiodes associated with TX1, TX3, and TX4 have the same integrationtime L2, while the photodiode associated with TX2 has the integrationtime L1. Thus, the photodiodes signals associated with TX1, TX3, andTX4, having the same integration time, can be combined into the FD node(binning) and read out together. Correspondingly shown with arrows inthe insert at the bottom right of FIG. 5G, signals from the photodiodeassociated with TX1(L2), the photodiode associated with TX3(L2), and thephotodiode associated with TX4(L2) can be binned.

FIGS. 6A, 6B, and 7-9 below illustrate a simplified configuration withrespect to the above-described HDR system to achieve two differentintegration times. FIG. 6A is the same as FIG. 1A and used forcomparison with FIG. 6B. FIG. 6B is a graphical representationillustrating a Bayer unit of a Quadrant Pixel HDR sensor from both topand side views, consistent with exemplary embodiments of the presentdisclosure. FIG. 6B is mostly similar to FIG. 1B, except that in eachpixel, two sub-pixels have a shorter integration time (S) and the othertwo have a longer integration time (L), and two photodiodes share a TXtransistor. Thus, in each pixel, four photodiodes corresponding to foursub-pixels can be configured to two groups having different integrationtimes. The grouping may be 2-2 or 1-3. Accordingly, in the side view,sub-pixels having the same integration time within a pixel may share thesame TX transistor, for example, by connecting their individual TXtransistors electrically with polysilicon or metal wire. Thus, theirsignals can be combined into a FD node together. Such structure may besimpler and easier to manufacture. Though this figure shows that twosub-pixels next to each other can be grouped and have the sameintegration time, it is also possible that two sub-pixels across thepixel are grouped to have the same integration time.

FIG. 7 is a circuit diagram illustrating a HDR sensor pixel with foursub-pixels and two different integration times, consistent withexemplary embodiments of the present disclosure. FIG. 7 is similar toFIG. 4, except that two photodiodes have the same integration time S andtheir corresponding transistors TX1 are electrically connected andcoupled to the same control line TX01, and the other two photodiodeshave the same integration time L and their corresponding transistors TX2are electrically connected and coupled to the same control line TX02.The working principles for the circuits in FIG. 7 are similar to thecircuit in FIG. 4, except that the TX1 s for PD1 and PD2 are controlledby one control line TX01 and TX2 s for PD3 and PD4 are controlled by onecontrol line TX02.

FIG. 8 is a graphical representation illustrating readout timing for theHDR sensor in FIG. 7, consistent with exemplary embodiments of thepresent disclosure. FIG. 8 is similar to FIG. 5B except that only twophotodiode signal lines corresponding to TX01 and TX02 are shown. Thesignals may be read out similarly as described above. The workingprinciple shown in FIG. 8 is similar to that in FIG. 5B.

FIG. 9 is a graphical representation illustrating readout timing for theHDR sensor in FIG. 7 with two different integration times, consistentwith exemplary embodiments of the present disclosure. FIG. 9 is similarto FIG. 5C except that only two different integration timescorresponding TX1 and TX2 are shown. Thus, the two groups of photodiodesare each configured with an integration time to control the exposurelevels. The working principle shown in FIG. 9 is similar to that inFIGS. 5C-5H.

FIG. 10 is a flow diagram illustrating a method 1000 for HDR sensing,consistent with exemplary embodiments of the present disclosure. Themethod 1000 may include a number of steps, some of which may be optional(e.g., steps 1001, 1004, and 1005). Method 1000 may be performed by theHDR sensing device or system described herein. As shown above, thesensing device may comprise an array of Bayer-pattern units of opticalfilters, each of the optical filters corresponding to a pixel of thesensing device, and each of the optical filters overlapping with aplurality of photodiodes. Method 1000 may focus on describing steps withrespect to a single pixel. Similarly, such steps may be performed onmultiple pixels across a sensing device.

At step 1001, photons may be received and directed to an optical filtervia a plurality of micro lenses (e.g., four micro lenses arranged in a 2by 2 configuration above optical filter).

At step 1002, the photons may be filtered through the optical filter.

At step 1003, the photons may be collected at a plurality of photodiodesassociated with the micro lenses and the optical filter (e.g., fourphotodiodes disposed below the optical filter and substantially alignedwith the four micro lenses respectively). Detailed configurations may bereferred to FIG. 1B described above. The photons may be converted tocharges and the charges accumulate at the photodiode.

At step 1004, the integration times of the plurality of photodiodes areindividually controlled via a circuit coupled to the photodiodes. Thecircuit may be referred to FIG. 3, FIG. 4, and FIG. 7 above. In someembodiments, at least two of the integration times of the plurality ofphotodiodes in each pixel may be different. In some embodiments, withthe structure shown in FIG. 1B, the four photodiodes in one pixel mayeach have different integration time. A user may also configure thecircuit to have two, three, or four out of the four photodiodes in theone pixel to have the same integration time. In view of the disclosure,such configurations should be able to achieve by a person havingordinary skill in the art.

At step 1005, signals of the photodiodes having different integrationtimes may be read out separately, and signals of photodiodes having thesame integration time may be combined and read out together via thecircuit.

FIGS. 11-14 describe RGB-NIR HDR sensing systems, devices, and methodswith various integration times. The RGB-NIR HDR sensing system may beconfigured to capture images covering both visible and NIR wavelengths.FIG. 11A is a graphical representation 1110 illustrating a Bayer unit ofa RGB-NIR (Red Green Blue-Near Infrared) sensor from both top and sideviews. FIG. 11A is similar to FIG. 1A, except that one of the greenfilters is replaced with a NIR filter. With a similar working principleas the other optical filters, a NIR filter allows light of apre-determined wavelength band to pass through and blocks light withother wavelengths. As shown in the top view, each Bayer unit comprises agreen filter, a blue filter, a red filter, and a NIR filter, eachcorresponding to a pixel of the Bayer unit. As shown in the side view,each optical filter has a μlens disposed above and a photodiode disposedbelow. Though the replacement of the green pixel with the NIR pixel inFIG. 11A allows some NIR detection, resolving power, luminance response,and signal-to-noise ratio (SNR) performance are sacrificed.

FIG. 11B is a graphical representation 1120 illustrating a Bayer unit ofa Quadrant Pixel RGB-NIR HDR sensor from both top and side views,consistent with exemplary embodiments of the present disclosure.Graphical representation 1120 shows four pixels each of width X, thefour pixels forming the Bayer unit. Each pixel may comprise multiplesub-pixels of width Y. In this figure, each pixel of width X comprisesfour sub-pixels of width Y. Each sub-pixel corresponds to a photodiode.Each photodiode may be coupled to a switch, for example a transistor, ina specific example, a charge transferring (TX) transistor, whichregulates an integration time of the photodiode. Each pixel may alsoinclude various optical filters as described below.

The top view of FIG. 11B shows an array of filter combinations, e.g.,configurations of filters. From the top view as shown, the Bayer unitmay comprise four pixels (e.g., a pixel 1121, etc.). Each pixel maycorrespond to one optical filter combination. Each pixel may comprisefour sub-pixels (e.g., the pixel 1121 comprises sub-pixels 1122, 1123,1124, and 1125). For each pixel, one or more sub-pixels may correspondto a wavelength band and the other sub-pixel(s) may correspond toanother wavelength band (e.g., sub-pixels 1122, 1123, and 1124correspond to green, and sub-pixel 1125 corresponds to NIR). Thecorresponding wavelength band may determine the associated opticalfilter (e.g., sub-pixels 1122, 1123, and 1124 comprise a green filter,sub-pixel 1125 comprises a NIR filter, and the green filter and the NIRfilter can be called an optical filter combination). In someembodiments, the NIR filter may be a square filter of width Y. The greenfilter may comprise three square filters each of width Y. Alternatively,the green filter may be a single filter, as if combining three squarefilters to form a single L-shaped and materially uniform green filterwith length X on each side. Thus, for this green pixel, three quartersof the green pixel corresponds to a green filter (shown as covered bywhite dotted oblique lines), and the rest quarter of the green pixelcorresponds to a NIR filter (shown as covered by black oblique dottedlines). In other words, the filter combination for the green pixelincludes one or more green filters covering three green sub-pixels, andone NIR filter covering a NIR sub-pixel. The width Y and width X canhave various lengths. An exemplary length for Y is 1.5 μm, and anexemplary length for X is 3.0 μm. Each of the sub-pixels comprises aμlens represented by a circle. Each of the sub-pixels may be labeled bya corresponding light band (e.g., red, green, blue, or NIR) and anintegration time (e.g., L_(NIR), L3, L2, or L1). Similar to the greenpixel described above, other pixels of the Bayer unit may be configuredaccordingly.

The μlens-optical filter-photodiode configuration in the verticaldirection is shown in the side view. Each photodiode may be paired witha corresponding μlens and an optical filter, all of which are associatedwith a pre-determined wavelength band (e.g., the associated μlens andoptical filter may all be transparent to NIR, and the photodiode candetect NIR light). The optical filter is disposed between the photodiodeand the μlens. In this side view, only one row of the sub-pixels areshown, and sub-pixels next to each other are of different wavelengthbands, and therefore, their corresponding optical filters are different.In some other embodiments, if sub-pixels next to each other are of thesame wavelength band, they may share the same optical filter (e.g., asingle piece of materially uniform optical filter covering two or moresub-pixel photodiodes). Thus, in an exemplary two by two arrangement,each pixel has four μlenses above a optical filter combination, fourphotodiodes below the optical filter combination, and four TXtransistors respectively coupled to the four photodiodes. The opticalfilter combination may comprise a square NIR filter and a L-shapedoptical filter (e.g., a blue, red, or green optical filter). TheL-shaped optical filter may be a single materially uniform filter as ifcombining three squares in a “L”. Thus, when the NIR filter is combinedwith the L-shaped optical filter, a large square-shaped optical filtercombination is obtained for each pixel. Further, each μlens may besubstantially aligned with its corresponding photodiode, such that mostof the photons impinging on the μlens can be directed to pass the filterand be detected by the photodiode.

In some embodiments, one or more of the μlens, optical filter, andphotodiode in each sub-pixel may selectively work at a predeterminedwavelength band (e.g., red, NIR, etc.), such that only the predeterminedwavelength band is detected. For example, the μlenses and thephotodiodes may cover both visible and NIR wavelength, as long as thecorresponding filters can select wavelength bands for detection. Aperson having ordinary skill in the art should be able selectphotodiodes with particular materials sensitive to certain wavelengths.For example, photodiodes that are sensitive to visible light can beplaced under RGB filters. Photodiodes that are sensitive to infraredlight, or particularly to near infrared light, such as siliconphotodiodes (with broad detection spectrum and particular thickness) canbe placed under the NIR filter.

As shown in the side view, each sub-pixel has a μlens disposed above thefilter and a photodiode disposed below the filter. When light impingeson the sensor, the μlens directs the light/photons to pass through thefilter and then to the photodiode, which generates charges (e.g.,electrons and holes) in response to the light exposure. Movement of suchcharges creates a current. To determine how much light/photons hits thesensor, the current is to be measured. The currents produced by thephoton conversion are typically very small, which discourages anaccurate direct measurement. Thus, current integration may be achievedby setting the voltage across the photodiode to a known potential, andusing the photodiode to collect photons for a period of time before thevoltage is read out. Longer integration time allows more charges to beconverted. The TX transistor coupled to the photodiode is used toregulate the integration time of the photodiode. Each photodiode may beassociated with a TX transistor. It is also possible that two or morephotodiodes couple to and share the same TX transistor.

In some embodiments, each sub-pixel is connected to a TX transistor forregulating integration times. By this way, the sub-pixels are providedwith individually-configurable differential effective integration timefor generating HDR images with the sensor. The various integration timesmay be labeled as L3, L2, L1, or L_(NIR). L3, L2, and L1 may correspondto different integration times from the longest to the shortest. L_(NIR)may be the same as or different from L3, L2, and L1. Though FIG. 11Bshows four sub-pixels with four integration times in each pixel, thenumber of sub-pixels in each pixel is not limited to four, and any twoof the integration times corresponding to the sub-pixels in each pixelmay be the same or different. Each of the integration times may be setin default, configured by users, or otherwise determined. Each of theintegration times may also be automatically configured according toluminance conditions (e.g., a longer exposure time is configured for adark condition by a luminance sensor and determination softwarealgorithm). Any of the sub-pixels of the same pixel may be configured tohave integration time L3, L2, L1, or L_(NIR), or any integration time asconfigured, which should not be limited to the illustrations in figuresherein. Integration time labels L in this disclosure are merelyexemplary. Also, in exemplary figures of this disclosure, the grey scaleof each sub-pixel may indicate the corresponding level of integrationtimes for illustration purposes. For example, L3 as having the longestintegration time may appear much brighter than L2, L1, or S having theshortest integration time. Again, the grey-scale illustration ofintegration times is merely exemplary and not tied to particularsub-pixels.

Further, the Bayer-pattern described herein may include variousmodifications in addition to those shown in FIGS. 11A and 11B. In someembodiments, the optical filters in a Bayer-pattern unit may include anycolor, such as CYGM (cyan, yellow, green, magenta), and RGBE (red,green, blue, emerald), etc. That is, the optical filters are not limitedto red, green, and blue filters. In some embodiments, multiple pixelsand corresponding filters in a Bayer-pattern unit may be oriented invarious configurations, e.g., rotated by 45 degrees. Therefore, anyincorporation of the claimed aspect to modified Bayer sensor designsstill falls in the scope of this disclosure. As such, each pixel can bedivided into any number of sub-pixels of any shapes, and each sub-pixelcan be individually controlled in terms of the integration time, therebyachieving multiple integration times within the same pixel.

In some embodiments, since each sub-pixel's integration time can beindividually controlled by the corresponding TX transistor, each pixelcan capture and convert image signals corresponding to four integrationtimes. The integration times may be the same or different. If the pixelhas more individually controlled sub-pixels, the image signals capturedcan correspond to more different integration times. Thus, even in onesensor detection by the disclosed device, each pixel can capturemultiple readings corresponding to different integration levels.Captured signals of short integration time may retain highlight detail(e.g., scenes with bright light) while captured signals of longintegration time may retain shadow detail (e.g., scenes with low light).These signals can be combined to obtain images and are essential toachieve HDR imaging. Further, with the incorporation of the NIRsub-pixel, NIR light can be captured along with the visible light toachieve NIR imaging.

A sensor may comprise an array of Bayer units, and each Bayer unit maycomprise an array of pixels as shown in FIG. 11B. Thus, in someembodiments, the disclosed sensing device may comprise an array ofoptical filter combinations. Each of the optical filter combinations maycorrespond to a pixel of the sensing device and have at least twodifferent filters (e.g., the green filter and the NIR filter), and eachof the optical filter combinations may be associated with a plurality ofphotodiodes (e.g., four photodiodes). Each of the filter combination maycomprise at least one Red-Green-Blue (RGB) filter and at least onenear-infrared (NIR) filter. The RGB filter may be a red color filter, agreen color filter, or a blue color filter. For example, the pluralityof photodiodes may comprise four photodiodes, at least one NIR filtermay cover one of the four photodiodes, and at least one RGB filter maycover three of the four photodiodes other than the photodiode covered byat least one NIR filter. The pixel may comprise four sub-pixels in a twoby two array, at least one NIR filter may correspond to one of the foursub-pixels, and at least one RGB filter may correspond to three of thefour sub-pixels other than the sub-pixel corresponding to at least oneNIR filter.

In some exemplary embodiments, for each Bayer pattern unit, as shown inFIG. 11B, a first pixel of the plurality of pixels may comprise one ormore first green filters covering one or more of the first pixel'sphotodiodes and may comprise a first near infrared (NIR) filter coveringone of the first pixel's photodiodes; a second pixel of the plurality ofpixels may comprise one or more blue filters covering one or more of thesecond pixel's photodiodes and may comprise a second NIR filter coveringone of the second pixel's photodiodes; a third pixel of the plurality ofpixels may comprise one or more red filters covering one or more of thethird pixel's photodiodes and may comprise a third NIR filter coveringone of the third pixel's photodiodes; and a fourth pixel of theplurality of pixels may comprise one or more second green filterscovering one or more of the fourth pixel's photodiodes and may comprisea fourth NIR filter covering one of the fourth pixel's photodiodes.Further, the one or more first green filters may be a single materiallyuniform filter, and the same may apply to the one or more blue filters,the one or more red filters, and the one or more second green filters.

FIG. 12 is a schematic circuit diagram illustrating a RGB-NIR HDR sensorsystem 1200, consistent with exemplary embodiments of the presentdisclosure. The system 1200 may comprise a pixel array 1201, a rowcontrol circuit 1202, a column readout circuit 1203, and a timinggenerator and processing circuit 1204. The pixel array 1201 may comprisemultiple pixels arranged by row and column and associated circuits,e.g., pixels shown in FIG. 11B. Each pixel row is coupled to row controlcircuit 1202, and each pixel column is coupled to the column readoutcircuit 1203. The row control circuit 1202 may control readout timing ineach row, and the column readout circuit 1203 may receive pixel signalsfrom each column. The timing generator and processing circuit 1204 maycontrol the row control circuit 1202 and the column readout circuit 1203in terms of clock timing, signal processing, etc. The above circuit ismerely exemplary, and other possible variations of circuit control maybe implemented.

During one exemplary exposure of the photodiode sensor, the photodiodesin the pixel array 1201 convert impinging photons into charges (e.g.,electrons and/or holes). The charges are integrated (collected) incorresponding sensor sub-pixels or pixels. After the completion ofintegration cycle, collected charges are converted into voltages. Thevoltages are supplied to the output terminals and coupled to columnreadout circuit 1203. In CMOS image sensors, the charge to voltageconversion is accomplished directly in the pixels themselves. The analogpixel voltage is transferred to the output terminals through variouspixel addressing and scanning schemes controlled by the row controlcircuit 1202. The analog signal can also be converted on-chip to adigital equivalent before reaching the chip output.

In some embodiments, the timing generator and processing circuit 1204may be configured to perform demosaicing and apply a chroma filter tothe white-balanced image signals from the column readout circuit 1203.The chroma filter may be applied to chroma de-noise the white-balancedimage signals from the column readout circuit 1203. The timing generatorand processing circuit 1204 may, for example, demosaic the image signalsand apply the chroma filter simultaneously, sequentially, or in aninterspersed manner. The chroma filter may increase noise correlationbetween image signals of each color (e.g., noise fluctuations in theblue, green, red and infrared channels may increase or decrease togetherin a correlated manner). For example, the timing generator andprocessing circuit 1204 may increase the correlated noise between theblue, green, red and infrared image signals. By increasing noisecorrelation, the timing generator and processing circuit 1204 may reducethe amount of noise amplification generated.

The pixels that are sensitive to light in the visible light spectrum(e.g., blue pixels, green pixels, red pixels, etc.) may sometimes bereferred to herein as visible light pixels. In scenarios where aninfrared filter is formed across each of the pixels in the pixel array1201, a portion of the image signals captured by the visible lightpixels (e.g., blue pixels, green pixels, red pixels, etc.) in the pixelarray 1201 may be generated in response to infrared light. Infraredlight captured by the visible image pixels can cause visible lightpixels to generate erroneous pixel values.

The timing generator and processing circuit 1204 may perform infraredimage signal contamination subtraction operations on the chroma filterand demosaicked image data. The timing generator and processing circuit1204 may determine an estimated value of the portion of the image signalof each color that was generated in response to infrared light. Thetiming generator and processing circuit 1204 may subtract the estimatedvalue from the image signals to remove the infrared light contributionto the image signals.

At the pixel level, corresponding portions of the row control circuit1202, the column readout circuit 1203, and/or the timing generator andprocessing circuit 1204 may be collectively deemed as “the circuitcoupled to the plurality of photodiodes” described below.

FIG. 13 is a circuit diagram illustrating a RGB-NIR HDR sensor pixelwith multiple sub-pixels and differential integration times, consistentwith exemplary embodiments of the present disclosure. The circuitdiagram of FIG. 13 may correspond to a pixel in FIG. 11B describedabove.

As shown in FIG. 13, dash regions indicate the four photodiodes (PD1,PD2, PD3, and PD4) of the four sub-pixels, each associated with anintegration time (L3, L2, L1, or L_(NIR)). As discussed above, anintegration time corresponds to the time for the correspondingphotodiode to collect charges caused by the impinging photons. Each ofthe photodiodes is coupled to a charge transferring (TX) transistor(TX1, TX2, TX3, or TX4), which may optionally operate in a pulsedintegration mode. Each TX transistor is coupled to a TX control line(e.g. transistor TX1 is coupled to TX01). The row control circuit 1202may provide charge transfer control signals through TX01, TX02, TX03,and TX04 to the gate terminal of each charge transferring transistorTX1, TX2, TX3, and TX4. For example, a first charge transfer controlsignal TX01 may be provided to charge transferring transistor TX1, asecond charge transfer control signal TX02 may be provided to chargetransferring transistor TX2, a third charge transfer control signal TX03may be provided to charge transferring transistor TX3, a fourth chargetransfer control signal TX04 may be provided to charge transferringtransistor TX4.

The four sub-pixels may share certain circuit architectures. Forexample, the sensor pixel may incorporate a buffer amplifier, typicallya source follower (SF) transistor, coupled to the TX transistors. The SFmay be coupled to a sense line (Vout) through a suitable addressingtransistor (also can be called a row select transistor RS). The TXtransistors are also coupled to a charge detection node (FD) (alsoreferred to as floating diffusion node or floating diffusion region).For example, one of the source or drain terminal of a TX transistor iscoupled to the photodiode, and the other is coupled to node FD. As shownin FIG. 13, TX1 is coupled between photodiode PD1 and the node FD, TX2is coupled between photodiode PD2 and the node FD, TX3 is coupledbetween photodiode PD3 and the node FD, and TX4 is coupled betweenphotodiode PD4 and the node FD.

The charge detection node FD may be implemented using a region of dopedsemiconductor (e.g., a doped silicon region formed in a siliconsubstrate by ion implantation, impurity diffusion, or other dopingtechniques). The FD region exhibits a capacitance that can be used todetect the charges that has been transferred from photodiodes. Thesignal associated with the detected charges on FD is applied to the gateof source-follower transistor SF and conveyed to row select transistorRS by source-follower transistor SF.

The FD node is coupled to a reset transistor (RST) that conductivelycouples the FD node to a voltage reference (VDDA). After the charge tovoltage conversion as described above is completed and the resultingsignal is transferred out from the sub-pixels/pixels through the senseline (Vout), the sub-pixels/pixel can be reset by the RST transistor foraccumulation of new charge. In the example shown in FIG. 13, transistorRS is controlled via line RS0. Transistor RST is controlled via lineRST0. This reset step removes collected charges, but may generatekTC-reset (thermal) noise. The kTC-reset noise is removed from thesignal by the Correlated Double Sampling (CDS) signal processingtechnique in order to achieve the desired low noise performance. CMOSimage sensors that utilize CDS usually require four transistors (4T) inthe pixel, one of which serves as the charge transferring (TX)transistor. It is possible to share some of the pixel circuittransistors among several photodiodes to reduce the pixel size.

In some embodiments, the circuit depicted in FIG. 13 may be a part ofthe pixel array 1201, vertical circuit lines such as Vout and VDDA maycouple to the column readout circuit 1203 of FIG. 12, and horizontalcircuit lines such as RST0, RS0, TX01, TX02, TX03, and TX04 may coupleto the row control circuit 1202 of FIG. 12.

FIG. 14 is a graphical representation illustrating readout timing forthe RGB-NIR HDR sensor in FIG. 13 with differential integration times,consistent with exemplary embodiments of the present disclosure. FIG. 14shows signal lines for four TX transistors with respect to time,corresponding to four photodiodes of one pixel and corresponding tointegration times L3, L2, L1, and L_(NIR) described above. The TXtransistors may operate in a pulsed integration mode to exhibit desireddifferent integration times for HDR imaging. In this figure, the readoutfor each photodiode starts with the end of a previous TX readout pulseand ends with another TX readout pulse. Within that period, also knownas a frame, each TX gate may be associated with an integration time,configurable via clock and timing by the circuits described above.

The voltage across each of the photodiodes and their readout times maybe configured by pulses to the corresponding charge transferringtransistor TX to set the integration times shown in FIG. 13. For exampleTX2(L1) in FIG. 14, after the read out pulse (e.g., the first pulse atthe line TX2(L1) in FIG. 14), the charge transferring transistor (e.g.,TX2 in FIG. 13) can be turned on by a high voltage on control linesignal TX2(L1), and RST (referring to FIG. 13) can be turned on again,and charges in the corresponding photodiode (e.g., PD2) are thrown outfrom the photodiode through the charge transferring transistor TX2 to FD(referring to FIG. 13), and FD is reset to VDDA through reset transistorRST. When the charge transferring transistor (e.g., TX2) is low (turnedoff), charges are allowed to accumulate on the corresponding photodiode(e.g., PD2) for a period of time, shown in FIG. 14 as the integrationtime. When the control line signal TX2(L1) is pulsed, for example, thepulse at the end of line TX2(L1), the accumulated charges aretransferred to node FD, and are read out via SF and RS transistors asthe corresponding photodiode signal. The charge transferring transistors(e.g., TX1, TX2, TX3, and TX4) are controlled individually during oneframe between a readout and a previous readout. Here, each photodiode inthe pixel corresponding a charge transferring transistor has anintegration time configurable by a corresponding charge transferringgate timing as shown in FIG. 14. Each integration time may be set to anylength. Thus, according to various integration times, the convertedcharges are different for each of the four photodiodes, achievingdifferent exposure levels within the same pixel.

As shown above, integration times of four TXs can be controlledindependently to achieve HDR imaging with four different integrationtimes. Each of the plurality of photodiodes may be associated with anintegration time, and at least two photodiodes of the plurality ofphotodiodes associated with the same optical filter have differentintegration times. In some embodiments, the plurality of photodiodescomprise four photodiodes, and at least three of the four photodiodesare each associated with a different integration time. In someembodiments, each of the plurality of photodiodes is coupled to aswitch, and the length of the integration time is controlled by theswitch. In some embodiments, similar to the modifications describedabove, it is also possible to achieve three different integration timesby setting two photodiodes to have the same integration times, orachieve two different integration times by setting two photodiodes tohave the same integration time and setting the other two photodiodes tohave another same integration time. Also, the signal charges in thephotodiodes can be combined into the FD node (binning) as describedabove. The binning method can increase the readout efficiency and signalto noise ratio.

Further, based on the disclosure, the NIR filter can be replaced with anIR filter to achieve a RGB-IR HDR sensing system. Alternatively, the NIRfilter can be replaced with any other optical filter according to theapplication. Moreover, any of the optical filters (green, red, and blue)can be replaced with NIR or IR filters.

Some existing HDR imaging systems (known as exposure bracketing) capturemultiple images with the image sensor, each image having a differentexposure time. This capturing process may take tens of milli-seconds. Inthis case, performing HDR imaging by combining the captured images maygenerate undesirable motion artifacts. The disclosed system can capturemulti-exposure-level images in one exposure detection. Since onedetection takes much less time (e.g., under a few milli-seconds) thanmultiple detections (e.g., tens of milli-seconds), motion artifactscaused by movements can be minimized. In another word, the disclosedsystem can integrate the times-domain HDR function with minimized motionartifact and multiple integration times in both RGB and RGB-IR sensingsystems and devices.

The specification has described methods, apparatus, and systems for HDRsensing or imaging. As shown above, each pixel may comprise foursub-pixels to achieve 2-4 different integration times within the samepixel. Similarly, each pixel can be divided into n sub-pixels to achieve1 to n different integration times, with n being any natural number andas long as the fabrication permits. The illustrated steps are set out toexplain the exemplary embodiments shown, and it should be anticipatedthat ongoing technological development will change the manner in whichparticular functions are performed. Thus, these examples are presentedherein for purposes of illustration, and not limitation. For example,steps or processes disclosed herein are not limited to being performedin the order described, but may be performed in any order, and somesteps may be omitted, consistent with the disclosed embodiments.Further, the boundaries of the functional building blocks have beenarbitrarily defined herein for the convenience of the description.Alternative boundaries can be defined so long as the specified functionsand relationships thereof are appropriately performed. Alternatives(including equivalents, extensions, variations, deviations, etc., ofthose described herein) will be apparent to persons skilled in therelevant art(s) based on the teachings contained herein. Suchalternatives fall within the scope and spirit of the disclosedembodiments.

While examples and features of disclosed principles are describedherein, modifications, adaptations, and other implementations arepossible without departing from the spirit and scope of the disclosedembodiments. Also, the words “comprising,” “having,” “containing,” and“including,” and other similar forms are intended to be equivalent inmeaning and be open ended in that an item or items following any one ofthese words is not meant to be an exhaustive listing of such item oritems, or meant to be limited to only the listed item or items. It mustalso be noted that as used herein and in the appended claims, thesingular forms “a,” “an,” and “the” include plural references unless thecontext clearly dictates otherwise.

It will be appreciated that the present invention is not limited to theexact construction that has been described above and illustrated in theaccompanying drawings, and that various modifications and changes can bemade without departing from the scope thereof. It is intended that thescope of the invention should only be limited by the appended claims.

What is claimed is:
 1. A sensing device, comprising: a plurality ofpixels, wherein each of the pixels comprises a plurality of photodiodes;wherein at least one of the photodiodes in each pixel is configured todetect non-visible light; wherein at least two of the photodiodes ineach pixel are configured to detect visible light; and wherein in eachpixel, a single color filter covers the photodiodes configured to detectvisible light.
 2. The sensing device of claim 1, further comprising: aBayer pattern unit, wherein the Bayer pattern unit includes theplurality of pixels.
 3. The sensing device of claim 2, wherein: theplurality of pixels in one Bayer pattern unit comprise four pixels in atwo by two configuration; and the plurality of photodiodes in one pixelcomprise four photodiodes in the two by two configuration.
 4. Thesensing device of claim 1, wherein: each of the photodiodes in eachpixel is associated with an integration time; and at least twophotodiodes in each pixel have different integration times.
 5. Thesensing device of claim 4, wherein: the integration time corresponds totime for the corresponding photodiode to collect charges caused byimpinging photons.
 6. A sensing device, comprising an array of opticalfilter combinations, wherein each of the optical filter combinationscorresponds to a pixel of the sensing device and has at least twodifferent filters, and wherein each of the optical filter combinationsis associated with a plurality of photodiodes; wherein one of thefilters is a single color filter covering a plurality of photodiodesconfigured to detect visible light; and wherein one of the filters is anon-visible light filter covering a photodiode configured to detectnon-visible light.
 7. The sensing device of claim 6, further comprising:a Bayer pattern unit, wherein the Bayer pattern unit includes four ofthe pixels.
 8. The sensing device of claim 6, wherein: at least one ofthe pixels comprises four of the photodiodes; the non-visible lightfilter covers one of the four photodiodes; and the single color filtercovers three of the four photodiodes other than the photodiode coveredby the non-visible light filter.
 9. The sensing device of claim 8,wherein: the four photodiodes are arranged in a two by two array. 10.The sensing device of claim 9, wherein the single color filter is amaterially uniform filter.
 11. The sensing device of claim 6, wherein:at least one of the pixels comprises four of the photodiodes; thesensing device further comprises four micro lenses respectivelyassociated with the four photodiodes; the four photodiodes are disposedin a two by two configuration under the optical filter combination; thefour micro lenses are disposed in the same two by two configurationabove the optical filter combination; and each micro lens is configuredto direct impinging light to pass through a part of the optical filtercombination to reach the corresponding photodiode.
 12. The sensingdevice of claim 6, wherein: each of the plurality of photodiodesassociated with one optical filter combination is associated with anintegration time; and at least two photodiodes of the plurality ofphotodiodes associated with the one optical filter combination havedifferent integration times.
 13. The sensing device of claim 12,wherein: the integration time corresponds to time for the correspondingphotodiode to collect charges caused by impinging photons.
 14. Thesensing device of claim 12, wherein: the plurality of photodiodesassociated with one optical filter combination comprise fourphotodiodes; and at least three of the four photodiodes are associatedwith different integration times.
 15. The sensing device of claim 12,wherein: each of the photodiodes is coupled to a switch; and the lengthof the integration time is controlled by the switch.
 16. The sensingdevice of claim 12, wherein signals of photodiodes having differentintegration times are read out separately; and signals of photodiodeshaving the same integration time are combined and read out together. 17.A sensing device, comprising a plurality of pixels, each comprising fourphotodiodes, at least two of the photodiodes in each pixel beingconfigured to detect visible light, and at least one of the photodiodesin each pixel being configured to detect non-visible light; and in eachpixel, a single color filter covering the plurality of photodiodesconfigured to detect visible light.
 18. The sensing device of claim 17,further comprising: a Bayer pattern unit, wherein the Bayer pattern unitincludes four of the pixels.
 19. The sensing device of claim 17,wherein: each of the four photodiodes in one pixel is coupled to atransistor for controlling an integration time of the photodiode. 20.The sensing device of claim 17, wherein: each of the four photodiodes isassociated with an integration time; and at least two of the photodiodesare associated with different integration times.